Reading mode: Light Dark

31/1.8 - Take 2

Go to last post
M

mmphilip

Member
Messages
47
Reaction score
1
Location
MI, US
Hello!

A couple weeks ago I purchased a FA 31mm to replace my Sigma 30/1.4. When it arrived the focusing barrel was very loose and wobbly (and got looser and wobblier over the few days I owned the lens) and backfocused badly. So I returned it for a replacement.

The new one arrived, and before I'm told to "stop doing tests and start taking pictures", let me say that's exactly what I did. The lens arrived, I put it on my camera, and went to the nearby horticultural gardens. I was mainly shooting at F/1.8 since my primary interest is its performance wide open. I immediately felt like something wasn't right. Even through the LCD the pictures looked soft and hazy, like I was taking them through a dirty window (the lens elements themselves are beautifully clear). Viewing the images on my computer confirmed my initial feeling.

So then I did some tests, though nothing fancy. Both at about 18 inches, 45 degree angle from subject (the subject is a refrigerator magnet listing 100 ways to praise you child). ISO 100, tripod, SR off, F/1.8, 1/500th. Adjusted white balance to make them black and white. Minor adjustments to match exposures. I believe this is apples to apples:

Pentax 31mm F/1.8





Sigma 30mm F/1.4





IMO, the Sigma blows the Pentax out of the water. I could believe that the Sigma might perform a littler better because it's stopped down 2/3 stop while the Pentax is wide open, but the difference, especially in the contrast, is huge.

So, my question is not whether to return the lens or not. I'm going to return it. The question is whether you think the lens is a bad copy or if I expect too much from from this lens. If this is par for the course, then I'll stick with the Sigma for now.

If you think it's a bad copy (which is what I think), here's another question: how many times must I return this lens for a new copy before getting a good one? Okay, that's not really answerable. How many times have you returned a lens before getting a satisfactory copy? I ordered this one and the previous one from B&H, which makes exchanges easy (though I hope Pentax reimburses them for shipping!). Should I return it altogether, wait six months, and then buy one from a different lot?

Deep thoughts? Sage advice? Thanks!
 
well it looks nothing i had seen from a good copy of this lens and if you read some tests online they would confirm it should have done better. There is another less satisfactory option meaning you keep the lens and send it straight to Pentax for adjustment after all you get 1 year warranty, i know it means you owe something you can't use right away but ones it gets fixed this lens might be worth a wait in the end. I would send it back though and try one more time but record a serial number just to make sure you are not getting same lens back from them or maybe try a different but still respectable place. Good luck.
--
Grzegorz

The camera is for life and for people, the swift and intense moments of life. - Ansel Adams
http://www.flickr.com/photos/7167702@N03/
 
mmphilip said:
Hello!

A couple weeks ago I purchased a FA 31mm to replace my Sigma 30/1.4. When it arrived the focusing barrel was very loose and wobbly (and got looser and wobblier over the few days I owned the lens) and backfocused badly. So I returned it for a replacement.

The new one arrived, and before I'm told to "stop doing tests and start taking pictures", let me say that's exactly what I did. The lens arrived, I put it on my camera, and went to the nearby horticultural gardens. I was mainly shooting at F/1.8 since my primary interest is its performance wide open. I immediately felt like something wasn't right. Even through the LCD the pictures looked soft and hazy, like I was taking them through a dirty window (the lens elements themselves are beautifully clear). Viewing the images on my computer confirmed my initial feeling.

So then I did some tests, though nothing fancy. Both at about 18 inches, 45 degree angle from subject (the subject is a refrigerator magnet listing 100 ways to praise you child). ISO 100, tripod, SR off, F/1.8, 1/500th. Adjusted white balance to make them black and white. Minor adjustments to match exposures. I believe this is apples to apples:

Pentax 31mm F/1.8





Sigma 30mm F/1.4





IMO, the Sigma blows the Pentax out of the water. I could believe that the Sigma might perform a littler better because it's stopped down 2/3 stop while the Pentax is wide open, but the difference, especially in the contrast, is huge.

So, my question is not whether to return the lens or not. I'm going to return it. The question is whether you think the lens is a bad copy or if I expect too much from from this lens. If this is par for the course, then I'll stick with the Sigma for now.

If you think it's a bad copy (which is what I think), here's another question: how many times must I return this lens for a new copy before getting a good one? Okay, that's not really answerable. How many times have you returned a lens before getting a satisfactory copy? I ordered this one and the previous one from B&H, which makes exchanges easy (though I hope Pentax reimburses them for shipping!). Should I return it altogether, wait six months, and then buy one from a different lot?

Deep thoughts? Sage advice? Thanks!
Click to expand...
I haven't personally used the Pentax 31mm f/1.8, but according to Photozone.de the Sigma 30mm is sharper in the center at all apertures, but much worse at the edges at f/2.8 and above.

If you shoot centered subjects the Sigma 30mm is likely the better choice. Is it as good overall as the Pentax? Probably not. Depends on your usage profile. The amazing thing about the 31mm is it is as sharp at the corners as it is in the center. The Sigma is very poor at the corners. I will review the 31mm once I get my hands on one, but for now I have the Sigma 30mm f/1.4 since it cost 1/3rd as much.

The Sigma 30mm f/1.4 earned its reputation from flaky focus performance with some cameras (mostly because it has a fair amount of field curvature and is f/1.4 and difficult to focus anyway). It outresolves my K-7 in the f/2-4 range, I often get what look like sharpening artifacts on fine lines, etc (in RAW).

The Pentax 31mm is like a Leica lens in a way, it is good, renders nicely, but you pay for it. The Sigma 30mm also renders really nicely and is a lot cheaper and 1/2 stop larger aperture.

Here is my review of the 30 if you haven't seen it:
http://erphotoreview.com/wordpress/?p=3

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)
 
Broda said:
well it looks nothing i had seen from a good copy of this lens and if you read some tests online they would confirm it should have done better. There is another less satisfactory option meaning you keep the lens and send it straight to Pentax for adjustment after all you get 1 year warranty, i know it means you owe something you can't use right away but ones it gets fixed this lens might be worth a wait in the end. I would send it back though and try one more time but record a serial number just to make sure you are not getting same lens back from them or maybe try a different but still respectable place. Good luck.
--
Grzegorz

The camera is for life and for people, the swift and intense moments of life. - Ansel Adams
http://www.flickr.com/photos/7167702@N03/
Click to expand...
I've considered keeping it and sending it to Pentax for servicing, but I'm inclined to agree that one more try for an copy that's acceptable out-of-the-box is the way to go. I just want to be sure that my expectations aren't too high, and it sounds like you don't think they are. Thanks for you comments.
 
viking79 said:
mmphilip said:
Hello!

A couple weeks ago I purchased a FA 31mm to replace my Sigma 30/1.4. When it arrived the focusing barrel was very loose and wobbly (and got looser and wobblier over the few days I owned the lens) and backfocused badly. So I returned it for a replacement.

The new one arrived, and before I'm told to "stop doing tests and start taking pictures", let me say that's exactly what I did. The lens arrived, I put it on my camera, and went to the nearby horticultural gardens. I was mainly shooting at F/1.8 since my primary interest is its performance wide open. I immediately felt like something wasn't right. Even through the LCD the pictures looked soft and hazy, like I was taking them through a dirty window (the lens elements themselves are beautifully clear). Viewing the images on my computer confirmed my initial feeling.

So then I did some tests, though nothing fancy. Both at about 18 inches, 45 degree angle from subject (the subject is a refrigerator magnet listing 100 ways to praise you child). ISO 100, tripod, SR off, F/1.8, 1/500th. Adjusted white balance to make them black and white. Minor adjustments to match exposures. I believe this is apples to apples:

Pentax 31mm F/1.8





Sigma 30mm F/1.4





IMO, the Sigma blows the Pentax out of the water. I could believe that the Sigma might perform a littler better because it's stopped down 2/3 stop while the Pentax is wide open, but the difference, especially in the contrast, is huge.

So, my question is not whether to return the lens or not. I'm going to return it. The question is whether you think the lens is a bad copy or if I expect too much from from this lens. If this is par for the course, then I'll stick with the Sigma for now.

If you think it's a bad copy (which is what I think), here's another question: how many times must I return this lens for a new copy before getting a good one? Okay, that's not really answerable. How many times have you returned a lens before getting a satisfactory copy? I ordered this one and the previous one from B&H, which makes exchanges easy (though I hope Pentax reimburses them for shipping!). Should I return it altogether, wait six months, and then buy one from a different lot?

Deep thoughts? Sage advice? Thanks!
Click to expand...
I haven't personally used the Pentax 31mm f/1.8, but according to Photozone.de the Sigma 30mm is sharper in the center at all apertures, but much worse at the edges at f/2.8 and above.

If you shoot centered subjects the Sigma 30mm is likely the better choice. Is it as good overall as the Pentax? Probably not. Depends on your usage profile. The amazing thing about the 31mm is it is as sharp at the corners as it is in the center. The Sigma is very poor at the corners. I will review the 31mm once I get my hands on one, but for now I have the Sigma 30mm f/1.4 since it cost 1/3rd as much.

The Sigma 30mm f/1.4 earned its reputation from flaky focus performance with some cameras (mostly because it has a fair amount of field curvature and is f/1.4 and difficult to focus anyway). It outresolves my K-7 in the f/2-4 range, I often get what look like sharpening artifacts on fine lines, etc (in RAW).

The Pentax 31mm is like a Leica lens in a way, it is good, renders nicely, but you pay for it. The Sigma 30mm also renders really nicely and is a lot cheaper and 1/2 stop larger aperture.

Here is my review of the 30 if you haven't seen it:
http://erphotoreview.com/wordpress/?p=3

Eric
--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)
Click to expand...
I've read the Photozone reviews, and in fact their review of the Sigma was probably my main reason for buying it a couple years ago. I really wanted that great center performance wide open. But now I'm looking for a better all-around performer, and according to the wisdom of the internet, the FA31 is as good as it gets. My other option, of course, is to keep the Sigma and supplement it with a vintage 28, 30, or 35mm for situations where autofocus and speed aren't as critical - and still save money. I'd really like a one lens solution, but I may go that route in the end. If I can find a FA31 that performs like my FA77 (which is also new and made in Vietnam), I'll be in hog heaven. That lens is fantastic!
 
MightyMike said:
The problem with returning a lens to get a good copy is that they'll likely just put the lens back on the shelf and sell it to someone else... you want a working lens send it in for servicing
--
Mike from Canada

'I like to think so far outside the box that it would require a telephoto lens just to see the box!' ~ 'My Quote :)'



http://www.airliners.net/search/photo.search?sort_order=views%20DESC&first_this_page=0&page_limit=180&&emailsearch=mighty_mike88%40hotmail.com&thumbnails=
Click to expand...
Yeah, I've thought of that very thing. I'm sure returned lenses don't go back to Pentax for service. They go back on the shelf. I'd be willing to part with the lens for a few weeks if I new it would come back in top notch shape, but I really fear that it would never perform as it should (or at least as I think it should). They might not even agree that it's underperforming at all and refuse to fix it.

I guess not everything can be easy. As mentioned in a previous post, I also have a recently purchased FA77. That lens was optical perfection (IMHO) right out of the box.

Thanks!
 
I also have got a bad copy of the 31 limited - a couple of years ago, when it was still produced si Japan; there was also a centering issue; I send it back to Pentax France, under warranty, they "calibrate" it but there was no visible improvement; therefore I asked for replacement, my second copy is very good.
Regards
--
jpgoube
 
that is a poor copy, on the basis of what i've seen. it must be irritating for you.

i used to own a sigma 30/1.4, and thought it a remarkable lens. i'm not sure i'd want a 31/1.8 after owning the siggie!
 
mmphilip said:
mmphilip wrote:

thing fancy. Both at about 18 inches, 45 degree angle from subject (the subject is a refrigerator magnet listing 100 ways to praise you child). ISO 100, tripod, SR off, F/1.8, 1/500th. Adjusted white balance to make them black and white. Minor adjustments to match exposures. I believe this is apples to apples:
Click to expand...
MF or AF?
 
Uluru said:
Uluru said:
mmphilip wrote:

thing fancy. Both at about 18 inches, 45 degree angle from subject (the subject is a refrigerator magnet listing 100 ways to praise you child). ISO 100, tripod, SR off, F/1.8, 1/500th. Adjusted white balance to make them black and white. Minor adjustments to match exposures. I believe this is apples to apples:
Click to expand...
MF or AF?
Click to expand...
AF
 
mmphilip said:
mmphilip said:
MF or AF?
Click to expand...
AF
Click to expand...
AF can miss at such short distance and you'll get an image like that above. Even if you try several times. Also, DOF at 31mm f1.8 and at such distance is some 1cm.

Can you try the MF instead, with a variety of subjects and distances? Perhaps your 31mm lens has a backfocus problem on your camera, you never know. Does GX allows for adjustments like K-7 does?

MF results compared to AF results will identify what's the case. Take your time, test it thoroughly.
 
mmphilip said:
I've read the Photozone reviews, and in fact their review of the Sigma was probably my main reason for buying it a couple years ago. I really wanted that great center performance wide open. But now I'm looking for a better all-around performer, and according to the wisdom of the internet, the FA31 is as good as it gets.
Click to expand...
The FA31mm is probably the better all round performer except the Sigma is probably a bit better near the center at large aperture. Which do you want? Depends on your subjects. I don't know if you really have a "bad" 31mm sample, it is probably just how it is. Primes can be bad, but unlikely.

Try the FA31mm on a real subject. What are you using it for, people? You might find that it is plenty sharp for the intended subjects. Side by side comparisons always make one lens look way worse than it really is.
mmphilip said:
My other option, of course, is to keep the Sigma and supplement it with a vintage 28, 30, or 35mm for situations where autofocus and speed aren't as critical - and still save money. I'd really like a one lens solution, but I may go that route in the end.
Click to expand...
A good lens to augment a Sigma 30mm f/1.4 would be a zoom lens like the 17-70 or 16-45 that performs very well around f/5.6. for landscapes, or even an older 30ish mm lens as you say.

Eric

--
I never saw an ugly thing in my life: for let the form of an object
be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://viking79.blogspot.com/ (Weekly)
Flickr Photostream: http://www.flickr.com/photos/28177041@N03/ (updated daily)
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad (8/31/09)
 
You must log in or register to reply here.

Keyboard shortcuts

f
Forum
m
My threads
Mobile site
About
Editorial content
Cameras & Lenses
Community
All content, design, and layout are Copyright © 1998–2025 Digital Photography Review All Rights Reserved.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
When you use DPReview links to buy products, the site may earn a commission.
©GPS Media - Guides, Products, Services.
Back
Top